For many financial advisors and investors, a simple approach to exchange-traded funds works best. A broad basket of low-cost funds representing the spectrum of core asset classes is all they’ll ever need. As a result, any fund not simply replicating an index can have a hard time gaining ETF investors’s attention.

But there are ample success stories among ETFs that target specific market niches. “Thematic” funds such as the ROBO Global Robotics and Automation Index ETF (ROBO), the Robotics & Artificial Intelligence ETF (BOTZ) and the ETFMG Prime Cyber Security ETF (HACK), for example, have each garnered roughly $2 billion in assets.

Todd Rosenbluth, director of ETF and mutual fund research at CFRA, says “there will always be a place for such thematic ETFs in a broader portfolio. The goal of outperforming drives some advisors and investors to focus on these kinds of opportunities.”

Indeed, solid performance helps draw attention. The above-mentioned three funds, for example, rose an average of 41 percent in 2017.

With a 39 percent return over the past 12 months, you’d suspect The Obesity ETF (SLIM) would hold great appeal to alpha-seeking investors. Yet with just $11.6 million in assets, this fund is clearly not on most investors’ radars. At least not yet.

Rosenbluth believes that investors want to see a fund like this build a longer track record before buying shares. The Obesity ETF won’t have a three-year track record until next June. With time, the fund’s strong performance should help it start to see more interest, adds Rosenbluth.

Looking For A Kickstart

Back in the heyday of the dot.com era, the Janus family of mutual funds gathered more than $300 billion in assets thanks to strong-performing tech-focused mutual funds. But Janus missed the boat as investors steadily migrated from mutual funds towards ETFs. Prior to recent mergers, assets under management had fallen by more than $100 billion.

To make up for lost time, the firm acquired ETF provider VelocityShares in 2014. That firm launched in 2009 and had amassed $2 billion by the time the link-up with Janus was announced.

Four years later, Janus Henderson (as the firm is now known) is still struggling for traction in the ETF marketplace. It has scored a winner with the Janus Henderson Short Duration Income ETF (VNLA), which has a healthy $569 million in assets. And a pair of smart beta funds have around $110 million in combined assets. But the four thematic ETFs it launched in June 2016 haven’t fared well on the AUM front. One of those funds, The Health and Fitness ETF, no longer exists, and the three remaining ETFs in this group have assets of just $11 million to $13 million, depending on the fund. Besides SLIM, the other two funds are The Organics ETF (ORG) and The Long-Term Care ETF (OLD).

Each of these funds pivots off a key demographic trend. The Obesity ETF aims to profit from the growing roster of companies that help address a surging health problem. The OECD predicts that 47 percent of Americans will be classified as obese by 2030. And on a global basis, roughly $2 trillion is being spent annually to tackle the co-morbidity issues related to obesity.

Companies in the SLIM portfolio must derive at least 50 percent of their sales or revenue from the treatment of diabetes, stroke, sleep apnea, high blood pressure, heart disease or cholesterol, says Nick Cherney, one of the founders of VelocityShares and now head of exchange-traded products at Janus Henderson. In addition, weight loss and or plus-size apparel businesses are eligible for inclusion in the fund.

The Obesity ETF, which carries a 0.50 percent expense ratio, deploys a modified market cap-weighted approach and is based on the underlying Solactive Obesity Index. The top holding in the index can’t exceed 20 percent, while other top holdings are rebalanced downward each quarter if they constitute more than five percent of the index. This year’s strong return for the fund is due to triple-digit gains in holdings such as Dexcom and Medifast.

Cherney has been tasked with helping Janus Henderson build greater traction in the ETF segment. It hasn’t been an easy lift.

“The ETF space is crowded, and to stand out you need a well-designed product, solid performance and the right distribution,” Cherney says.

And there’s another factor as well “It’s up to the firm to raise awareness of these funds, and Janus hasn’t yet given a lot of exposure to these funds,” says Rosenbluth.

Cherney is taking the long view with his company’s thematic funds. “We remain focused on funds that capture long-term trends that will play out over decades,” he says. “We think these thematic ETFs have a strong story behind them, and we need to just keep building awareness around them.”

This might become a case of success begetting success. As The Obesity ETF and other Janus Henderson thematic offerings build more assets over time, they may be seen as sufficiently viable and liquid for a growing pool of investors.